Processing, May 2018

Special Section Motors Drives High voltage motors O n e s i z e d o e s n o t f i t a l l Reliability is in the details of design testing experience and knowledge By Eerik Kinnunen ABB Motors and Generators igh voltage motors are generally engineered for their application One size does not fit all and getting it right depends on attention to detail This process includes H reviewing designs qualifying suppliers and testing outsourced components to improve outcomes and monitor the entire process Standardized rules must be set clear instructions should be produced and employees must be trained Above all experience and industry knowledge must be harnessed to find out what kind of motor will perform best in the application build it according to proven designs materials and methods and support it over its life cycle through a network of local service organizations Why do motors fail Like all machinery and equipment motors are subject to wear and tear Thermal electrical ambient and mechanical TEAM stresses cause components to deteriorate as they age Analyzing the causes of failure for motors from different manufacturers shows that problems with the bearings or stator winding insulation are behind the majority of failures See Table 1 for example failure statistics Manufacturers usually give special attention to these two areas to maximize the reliability of their motors However while this article focuses on bearings and insulation it also examines the vital role played by shaft rotor stator frame cooling system accessories and other components in overall reliability Engineering reliability into new product lines Manufacturers apply a range of reliability engineering techniques when developing new product lines Failure Modes and Effects Analyses FMEAs are conducted to predict what could potentially go wrong and identify the best ways to prevent it Parameters like strength fatigue and vibration levels are analyzed using advanced tools such as finite element method FEM The designs themselves are also subject to several reviews Because bearings and insulation are so important for overall reliability the research and development R D team at ABB includes personnel who concentrate specifically on these areas Furthermore the company has an in house insulation laboratory that executes the comprehensive testing of insulation materials support and other materials exposed to severe stresses Motors from various manufacturers rated 10 kW 5 15 kV Bearings 4177 Stator windings 1289 Rotor bars rings 764 Shaft or coupling 430 External device 1814 Not specified 1527 Note These figures cover induction motors deployed in the oil gas and petrochemical industries in the North Sea and Norway Source O V Thorsen and M Dalva A survey of faults on induction motors in offshore oil industry petrochemical industry gas terminals and oil refineries IEEE Transactions on Industry Applications vol 31 no 5 pp 1186 1196 Sept Oct 1995 Naturally product development involves extensive testing But in addition to the manufacturers own test field a test run of prototypes in real world operating conditions at customer sites is also helpful Sub components should be tested to check and validate new structures strength and fatigue and other properties Certain operating environments have their own special requirements For example where the new motors are targeted at the marine segment the prototypes have to be reviewed and tested by the relevant classification society Similarly motors for potentially explosive atmospheres are type tested according to international standards ensuring that they are spark free in all operational conditions 28 Processing MAY 2018 Table 1 Motor failure statistics

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